Pre-Implantation Genetic Diagnosis: Current Practice and Controversies

2,341 views

Published on

Dr Ken Maclean, Clinical Geneticist, from Primary Care Genetics has presented at the Obstetric Malpractice Conference. If you would like more information about the conference, please visit the website: http://bit.ly/10xh1iO

Published in: Health & Medicine
0 Comments
5 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
2,341
On SlideShare
0
From Embeds
0
Number of Embeds
2
Actions
Shares
0
Downloads
222
Comments
0
Likes
5
Embeds 0
No embeds

No notes for slide

Pre-Implantation Genetic Diagnosis: Current Practice and Controversies

  1. 1. • PGD is a reproductive genetic option, alongside:– Not conceiving– Donor gamete(s)– Adoption– Natural conception– Natural conception, prenatal diagnosis & termination ofpregnancy– PGD = IVF + ICSI + embryo biopsy + genetic analysis– Differentiates genetic constitution prior to transfer– genes & chromosomes (PGD vs PGS)
  2. 2. • PGD requires excellence in– Fertility Medicine– Clinical Genetics– Embryology– Molecular analysis– Embryo vitrification– Clinical support systems– Funding– IVF is the foundation stone of PGD
  3. 3. • Improve health & wellbeing of offspring• Minimise risk of inheriting serious disability• Typically fertile couples• Adjunct to IVF• Euploid vitrified embryo selection may:• Increase clinical pregnancy rate per embryo transfer• Reduce miscarriage rate• Reduce risk of IVF-related birth defects• Infertility may alter threshold for PGD• Disease predispositions
  4. 4. Intra-cytoplasmic sperm injection(ICSI)Extensive IVF & genetic work-up in PGD- karyotyping in IVFpreconceptional genetic screeningMultiple appointments & assessments
  5. 5. Laser-assisted hatchingDay 3 embryo: 1-2 cells(out of 4-8 cells)ORD5 embryo (blastocyst)3-5 trophectoderm cells from(future placenta)Inner cell mass (embryo) untouched
  6. 6. Methods for Preimplantation GeneticScreening and Diagnosis.Bodurtha J, Strauss JF III. N Engl J Med 2012;366:64-73.
  7. 7. DNA extraction & amplificationPCRpolymerase chainreactionGenetic analysis done on site or remotely (transport PGD)Blastocyst vitrification awaiting DNA test results
  8. 8. Array CGHtestinghttp://www.nature.com/scitable/topicpage/microarray-based-comparative-genomic-hybridization-acgh-45432Figure 1Source: Fertility and Sterility 2011; 95:953-958(DOI:10.1016/j.fertnstert.2010.09.010)+19/-22-10/-1646, XX
  9. 9. Contribution of individual chromosomesto aneuploidy in blastocystsFragouli et al. Fertil Steril 2010
  10. 10. Pregnancy outcomes# embryo transfers 39implantation rate (# implantations) 46% (18)<38yrs 56% (9/16)>38yrs 39% (9/23)Clinical pregnancy rate/oocyte retrieval 62% (18/29)<38yrs 75% (9/12)>38yrs 53% (9/17)
  11. 11. PGD limitations are technical &biologicalEmbryo mosaicismUntested embryoslow yield in IVF cyclefailure of laboratory testingDiscrepant results are uncommonEmbryo mosaicismLab errorOption of prenatal testing
  12. 12. GENEMutated genex
  13. 13. •  absence of the mutated geneMay be a failure of DNA amplificationOccurs in 5-10% of PGD testingx
  14. 14. Linkage analysis is best practice inPGD testing• Polymorphic short tandem repeats (STRs) that flank themutation/disease locus• Determine phasing by family study in PGD work-up• Highly accurate, highly reproducible: primary test in PGDGENEMarker 1 Marker 2 Marker 3 Marker 4Mutationx
  15. 15. Linkage/marker analysis inbeta-thalassaemiaaffected embryounaffected embryo
  16. 16. Methods for Preimplantation GeneticScreening and Diagnosis.Bodurtha J, Strauss JF III. N Engl J Med 2012;366:64-73.
  17. 17. • Single gene disorders• Disease & disability• Chromosome disorders– Chromosome translocations– Comprehensive chromosome screening (aneuploidy)• Trait selection• HLA matched stem cell source• Sex selection• Carrier status
  18. 18. Common PGD indications
  19. 19. The use of PGD is increasing
  20. 20. Initial PGD cycle may incur >10k out-of-pocket costs~6-9k for subsequent cycles
  21. 21. • IVF 30 year history– 2-3 million babies. Many are now parents– 1-2%Australian babies pa are conceived by IVF• PGD 15 year history• >1,000Australian PGD babies
  22. 22. • An excess risk of birth defects in IVF and ICSI infants is biologicallyplausible.• Factors associated that may increase the risk of birth defects include– the underlying causes of infertility in the couples– factors associated with the IVF/ICSI procedures– eg freezing and thawing of embryos– delayed fertilization of oocytes– culture media composition– medications used to induce ovulation or for luteal phase support– Endometrial milieu
  23. 23. The risk of major birth defects after intracytoplasmic sperminjection and in vitro fertilisationHansen et al NEJM 2002;346 (10):725-730Methods• Data obtained from three registries in Western Australia on births, births after assisted conception, and majorbirth defects in infants born between 1993 and 1997.• Assessed the prevalence of major birth defects diagnosed by one year of age in infants conceived naturally orwith use of intracytoplasmic sperm injection or in vitro fertilization.Results• Twenty-six of the 301 infants conceived with intracytoplasmic sperm injection (8.6 percent) and 75 of the 837infants conceived with in vitro fertilization (9.0 percent) had a major birth defect diagnosed by one year of age,as compared with 168 of the 4000 naturally conceived infants (4.2 percent; P<0.001 for the comparisonbetween either type of technology and natural conception).• As compared with natural conception, the odds ratio for a major birth defect by one year of age, was 2.0 (95percent confidence interval, 1.3 to 3.2) with intracytoplasmic sperm injection, and 2.0 (95 percent confidenceinterval, 1.5 to 2.9) with in vitro fertilization.• Infants conceived with use of assisted reproductive technology were more likely than naturally conceivedinfants to have multiple major defects and to have chromosomal and musculoskeletal defects.
  24. 24. • Systematic review all papers published by March 2003 with data relating to the prevalenceof birth defects in infants conceived following IVF and/or ICSI compared withspontaneously conceived infants• Twenty-five studies were identified for review. Two-thirds of these showed a 25% orgreater increased risk of birth defects in ART infants.• Size of ART group in each study ranged from 32-9111 infants• Additionally results of meta-analyses of the seven reviewer-selected studies and of all 25studies suggest a statistically significant 30–40% increased risk of birth defects associatedwith ART.• Pooled results from all suitable published studies suggested that children born followingART are at increased risk of birth defects compared with spontaneous conceptions• 1.3-fold risk
  25. 25. • Data analysed from the National Birth Defects Prevention Study, a population-based, multicenter, case–control study of birth defects.• NBDPS;10 states, investigates environmental and genetic risk factors for 30 major birth defects• Included mothers of fetuses or live-born infants with a major birth defect (case infants) and motherswho had live-born infants who did not have a major birth defect (control infants), delivered during theperiod October 1997–December 2003.• Study compared mothers who reported ART use (IVF or ICSI) with those who had unassistedconceptions.• 4792 control infants, 9584 case infants.• ART was reported by 51 (1.1% ) of all control mothers and 230 (2.4%) case mothersAmong singleton births, ART was associated with septal heart defects (adjusted odds ratio [aOR] 2.1,95% confidence intervals [CI] 1.1–4.0), cleft lip with or without cleft palate (aOR 2.4, 95% CI 1.2–5.1),oesophageal atresia (aOR 4.5, 95% CI 1.9–10.5) and anorectal atresia (aOR 3.7, 95% CI 1.5–9.1).Among multiple births, ART was not significantly associated with any of the birth defects studied.Findings suggest that surgically important birth defects occur more often among infantsconceived with ART
  26. 26. Epigenetic disordersPossible link to embryo culture
  27. 27. National Health and Medical Research CouncilEthical Guidelines on the use of assisted reproductivetechnology in clinical practice and researchS11: Do not select sex for non-medical purposes• Sex selection is an ethically controversial issue.• TheAustralian Health Ethics Committee (AHEC) believesthat admission to life should not be conditional upon achild being a particular sex.Therefore, pending furthercommunity discussion, sex selection (by whatever means)must not be undertaken except to reduce the risk oftransmission of a serious genetic condition….• Regulatory powers – clinic accreditation
  28. 28. State Laws Regulating Assisted Reproduction• NSW: Assisted ReproductiveTechnology Act 2007 &Assisted ReproductiveTechnology Regulations 2009• Victoria: Assisted ReproductiveTreatment Act 2008 &Assisted ReproductiveTreatment Regulations 2009• South Australia: Assisted ReproductiveTreatment Act1988 & Assisted ReproductiveTreatment Regulations2010• Western Australia: Human ReproductiveTechnology Act1991 & Human ReproductiveTechnology Act Directions2004
  29. 29. – http://www.retinaaustralia.com.au/images/X-linkedRecessive.gifPost-PGD risk (at 99% accuracy) 0.25%Post-PGD risk (at 90% accuracy) 2.5%
  30. 30. Victorian Assisted ReproductiveTreatmentAct 2008• Sex selection is prohibited in the following terms:s28 (1) A person carrying out a treatment procedure must not usegametes or an embryo, or perform the procedure in a particular way,with the purpose or a purpose of producing or attempting to producea child of a particular sex.Penalty: 240 penalty units or 2 years imprisonment or both.(2) Subsection (1) does not apply if—(a) it is necessary for the child to be of a particular sex so as to avoidthe risk of transmission of a genetic abnormality or a genetic diseaseto the child; or(b) the Patient Review Panel has otherwise approved the use of thegametes or embryo for the purpose or a purpose of producing orattempting to produce a child of a particular sex.
  31. 31. JS and LS v Patient Review Panel [2011]VCAT 856• “In our view, arguments based on completionof family, replacement of a child, or familybalance do not advance the welfare orinterests of a child born to fulfil that end.”

×